In algorithm design, what ensures that a solution will be reached eventually?

Logical flow is essential in algorithm design as it dictates the structured sequence in which instructions are carried out. It ensures that all steps of the algorithm are followed in a coherent manner that leads to a conclusion. When logical flow is maintained, the algorithm proceeds methodically through its defined processes, leading to a definitive outcome or solution.

The other concepts, while important in their own right, do not guarantee that a solution will be reached on their own. Decisions within an algorithm may create branches, leading to different paths of execution, but they don't inherently assure that a conclusion will be reached. Processes refer to the specific steps taken, but without a structured flow, these steps may not connect logically. Subroutines can encapsulate functionality, enhancing modularity, but they also rely on the overall logical flow to ensure that the algorithm concludes successfully.